lib: use destructuring for some constants

This change is to unify the declaration for constants into using
destructuring on the top-level-module scope, reducing some redundant
code.

PR-URL: https://github.com/nodejs/node/pull/16063


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>